A presence service allows users of the service to “Subscribe” to another person's availability. Users that view another person's availability are called “Watchers”. The user that projects their availability is called a “Presentity”. This is in conformance with the definitions used in IETF RFC 2778 on the Common Profile for Instant Messaging. A positive or negative acknowledgement to a subscription request is based on a set of availability notification policies that the Presentity can define.
Presence services currently offer two user capabilities:                1. Projection of Availability. This is the traditional user's availability information. It is an indication of the person's desire or willingness to communicate. The availability information is projected to other users. If the person is willing to communicate they will appear available. Otherwise, they appear as unavailable.        2. Communication Contact Information. This second type of information reflects how, where or by what means the person is available for communication. The contact information describes different communication service types that the person is currently available on. Examples of such communication types include telephony, Instant Messaging, chat, video streaming, etc.        
The inventors are aware of no literature on the use of roles for presence systems. All of the known presence systems deal solely with the availability of users rather than with abstract concepts like roles. Roles have, however, been used in other systems that are unrelated to user communications. For example, the American National Institute for Standards and Technology (NIST) has investigated Role-Based Access Control (RBAC), as described in U.S. Pat No. 6,023,765 (Kuhn) entitled Implementation of role Based Access Control in Multi-level Secure Systems. Most of this work though relates to security and access control for groups and persons in particular roles. For presence services, SUN's iPlanet Messaging Server [Sun Microsystems] claims to support the creation of groups, users and roles but does not provide the ability to subscribe to users in particular roles. Products also exist that use roles for workflow management [See K. Izaki, M. Takizawa, and K. Tanaka, Information Flow Control Role-Based Model for Distributed Objects, Proc. Int. Conf. Parallel Distributed Systems ICPADS, p 363-370, 2001” and J. Barkley, “Workflow Management Employing Role-Based Access Control”. U.S. Pat. No. 6,088,679, December 1997]. However, these products though do not leverage or reflect user availability, as is required in presence systems.